Exercise machine



FIG. 1 is a perspective view of an exercise machine showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a top plan view of thereof; and,

FIG. 5 is a left side elevational view of the exercise machine; the right side elevational view being a mirror image thereof. 

The ornamental design for an exercise machine, as shown and described. 